Vincenty's formulae

Vincenty's formulae are two related iterative methods, developed by Thaddeus Vincenty in 1975, used to calculate distances between points on the surface of a spheroid. Because they assume the Earth is an oblate spheroid rather than a perfect sphere, they are more accurate than methods based on a spherical Earth, such as the great circle distance. One formula, the direct method, finds a point's location given a starting point, a distance, and a direction, while the other, the inverse method, calculates the geographic distance and azimuth between two given points. The formulae have been widely used in geodesy because they are accurate to within about half a millimeter on the reference ellipsoid. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/